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MAXI/GSC detection of a new X-ray brightening of MAXI J1957+032/IGR J19566+0326

ATel #8143; J. Sugimoto (RIKEN), H. Negoro (Nihon U.), M. Sugizaki (RIKEN), S. Ueno, H. Tomida, S. Nakahira, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA), T. Mihara, M. Serino, M. Shidatsu, T. Takagi, M. Matsuoka (RIKEN), N. Kawai, M. Arimoto, T. Yoshii, Y. Tachibana, Y. Ono, T . Fujiwara (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Kawakubo, H. Ohtsuki (AGU), H. Tsunemi, R. Imatani (Osaka U.), M. Nakajima, K. Tanaka, T. Masumitsu (Nihon U.), Y. Ueda, T. Kawamuro, T. Hori (Kyoto U.), Y. Tsuboi, S. Kanetou (Chuo U.), M. Yamauchi, D. Itoh (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Morii (ISM), on behalf of the MAXI team
on 9 Oct 2015; 14:51 UT
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)

Subjects: X-ray, Binary, Black Hole, Neutron Star, Transient

Referred to by ATel #: 8146, 8149, 8197, 8529

At 12:24 UT on 2015 October 06 (MJD 57301), the MAXI nova alert system triggered an X-ray flux increase from the position consistent with the transient X-ray source, MAXI J1957+032/IGR J19566+0326. The source flux has gradually increased, and the daily averaged 2-20 keV X-ray flux reached 15.8 +/- 5.0 mCrab on October 7 (MJD 57302).

The source was first discovered on 2015 May 11, independently by MAXI (ATel #7504) and INTEGRAL (ATel #7506), and then the flux quickly decayed by 0.3-0.4 days (ATel #7520).

The nature of the source is quite unknown. So, we encourage multiwavelength follow-up observations of this source.

MAXI public archive for MAXI J1957+032